Imaging device and endoscopic device

ABSTRACT

An imaging device includes: first and second image sensors; a first communication controller configured to be connected to the first image sensor; a first clock generator that generates a first clock signal that is a reference for operation of the first communication controller; a second communication controller configured to be connected to the second image sensor; a second clock generator that generates a second clock signal that is a reference for operation of the second communication controller; a reference synchronization signal generator that generates a reference synchronization signal; and an imaging synchronization signal generator that generates an imaging synchronization signal which is a trigger for determining timings of imaging by the first and second image sensors, and outputs the imaging synchronization signal to the first and second communication controllers at a timing when a predetermined period of time has elapsed from a reference timing based on the reference synchronization signal.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of PCT international application Ser.No. PCT/JP2015/058379 filed on Mar. 19, 2015 which designates the UnitedStates, incorporated herein by reference, and which claims the benefitof priority from Japanese Patent Application No. 2014-128428, filed onJun. 23, 2014, incorporated herein by reference.

BACKGROUND

1. Technical Field

The disclosure relates to an imaging device including a plurality ofimage sensors, and to an endoscopic device.

2. Related Art

Endoscopic systems have been used to observe an organ of a subject suchas a patient in the medical field. The endoscopic system includes: anendoscope that includes an insertion unit provided with an image sensoron its tip, having flexibility and an elongated shape, and configured tobe inserted into a body cavity of the subject; and a processing devicethat is connected to the proximal end of the insertion unit through acable, processes an in-vivo image in accordance with the imaging signalsgenerated by the image sensor, and displays the in-vivo image, forexample, on a display unit.

A technique in which an endoscopic system is provided with a pluralityof image sensors including CMOS image sensors on a tip of an endoscopeso as to generate a three-dimensional image or generate a cleartwo-dimensional image based on the images taken by the image sensors hasbeen known (for example, Japanese Patent Application Laid-open No.2006-181021). For example, the image sensors are connected to aprocessing device through dedicated lines (parallel bus) so as totransmit signals in Japanese Patent Application Laid-open No.2006-181021. A timing generator generates a signal for driving the imagesensors using a common clock, and this synchronizes the image sensors inJapanese Patent Application Laid-open No. 2006-181021.

SUMMARY

In some embodiments, an imaging device includes: first and second imagesensors configured to receive light and to perform photoelectricconversion on the received light to generate electric signals; a firstcommunication controller configured to be connected to the first imagesensor to perform communication with the first image sensor and tocontrol the communication to perform operating control on the firstimage sensor; a first clock generator configured to generate a firstclock signal that is a reference for operation of the firstcommunication controller; a second communication controller configuredto be connected to the second image sensor to perform communication withthe second image sensor and to control the communication to performoperating control on the second image sensor; a second clock generatorconfigured to generate a second clock signal that is a reference foroperation of the second communication controller; a referencesynchronization signal generator configured to generate a referencesynchronization signal; and an imaging synchronization signal generatorconfigured to generate an imaging synchronization signal that is atrigger for determining timings of imaging by the first and second imagesensors, and to output the imaging synchronization signal to the firstand second communication controllers at a timing when a predeterminedperiod of time has elapsed from a reference timing based on thereference synchronization signal. When the first and secondcommunication controllers perform synchronization control communicationsfor synchronizing the timings of imaging by the first and second imagesensors, the first and second communication controllers are configuredto determine the timings of imaging by the first and second imagesensors using the imaging synchronization signal output from the imagingsynchronization signal generator as a trigger.

In some embodiments, an endoscopic device includes: an insertion unitthat has an elongated shape and is configured to be inserted into aliving body; first and second image sensors configured to receive lightand to perform photoelectric conversion on the received light togenerate electric signals; a first communication controller configuredto be connected to the first image sensor to perform communication withthe first image sensor and to control the communication to performoperating control on the first image sensor; a first clock generatorconfigured to generate a first clock signal that is a reference foroperation of the first communication controller; a second communicationcontroller configured to be connected to the second image sensor toperform communication with the second image sensor and to control thecommunication to perform operating control on the second image sensor; asecond clock generator configured to generate a second clock signal thatis a reference for operation of the second communication controller; areference synchronization signal generator configured to generate areference synchronization signal; and an imaging synchronization signalgenerator configured to generate an imaging synchronization signal thatis a trigger for determining timings of imaging by the first and secondimage sensors, and to output the imaging synchronization signal to thefirst and second communication controllers at a timing when apredetermined period of time has elapsed from a reference timing basedon the reference synchronization signal. When the first and secondcommunication controllers perform synchronization control communicationsfor synchronizing the timings of imaging by the first and second imagesensors, the first and second communication controllers are configuredto determine the timings of imaging by the first and second imagesensors using the imaging synchronization signal output from the imagingsynchronization signal generator as a trigger.

The above and other features, advantages and technical and industrialsignificance of this invention will be better understood by reading thefollowing detailed description of presently preferred embodiments of theinvention, when considered in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of the configuration of an endoscopicsystem according to a first embodiment of the present invention;

FIGS. 2A and 2B are schematic block diagrams of the configuration of theendoscopic system according to the first embodiment of the presentinvention;

FIG. 3 is a timing chart of the control timing of the endoscopic systemaccording to the first embodiment of the present invention;

FIG. 4 is a timing chart of the control timing of the endoscopic systemaccording to the first embodiment of the present invention, illustratinga part of FIG. 3 in more detail;

FIGS. 5A and 5B are schematic block diagrams of the configuration of anendoscopic system according to a second embodiment of the presentinvention; and

FIG. 6 is a timing chart of the control timing of the endoscopic systemaccording to the second embodiment of the present invention.

DETAILED DESCRIPTION

Modes for carrying out the present invention (hereinafter, referred toas “embodiment(s)”) will be described below. A medical endoscopic systemthat takes an image of the inside of the body cavity of a subject suchas a patient and displays the image will be described in the embodimentsas an exemplary system including the imaging device and endoscopicdevice according to the present invention. The present invention is notlimited to the embodiments. The same reference signs are used todesignate the same elements throughout the drawings.

First Embodiment

FIG. 1 is a schematic diagram of the configuration of an endoscopicsystem according to a first embodiment of the present invention. FIGS.2A and 2B are schematic block diagrams of the configuration of theendoscopic system according to the first embodiment of the presentinvention.

An endoscopic system 1 illustrated in FIG. 1 and FIGS. 2A and 2Bincludes: an endoscope 2 whose tip is configured to be inserted into abody cavity of a subject to capture an in-vivo image of the subject; aprocessing device 3 that processes the in-vivo image taken with theendoscope 2 in a predetermined image process, and generally controls theoperations of the whole endoscopic system 1; a light source device 4that generates an illumination light to be emitted from the tip of theendoscope 2; and a display device 5 that displays the in-vivo imageprocessed with the processing device 3.

The endoscope 2 includes: an insertion unit 21 that has flexibility andelongated shape; an operating unit 22 that is connected to the proximalend of the insertion unit 21 so as to receive the input of variousoperation signals; and a universal cord 23 that extends in a directionopposite to the direction in which the insertion unit 21 extends fromthe operating unit 22, includes connectors 23 a and 23 b connected tothe processing device 3 and the light source device 4, respectively, andincorporates various cables therein.

The insertion unit 21 includes a tip portion 24 that incorporates animage sensor in which pixels, which generate signals by receiving lightand performing photoelectric conversion on the received light, aretwo-dimensionally arranged; a curved portion 25 that is formed by aplurality of curved bridges and can curve freely; and a long flexiblepipe portion 26 that is connected to the proximal end of the curvedportion 25.

The tip portion 24 includes a light guide 241, an illumination lens 242,two optical systems (optical systems 243A and 243B), a first imagesensor 244A, and a second image sensor 244B.

The light guide 241 is made, for example, of glass fiber and is a lightguiding path for light emitted from the light source device 4. Theillumination lens 242 is a lens that is provided on a tip of the lightguide 241 and emits the illumination light.

The optical systems 243A and 243B are configured to collect light. Eachof the optical systems 243A and 243B includes one or plurality oflenses. The optical systems 243A and 243B can have an optical zoomfunction to vary the angle of view or a focus function to vary the focalpoint.

Each of the first image sensor 244A and the second image sensor 244Bincludes: a sensor unit 244 a that performs photoelectric conversion onthe light collected by each of the optical systems 243A and 243B andgenerates an electric signal (hereinafter, referred to as an imagingsignal); an analog front end unit 244 b (hereinafter, referred to as an“AFE unit 244 b”) that removes noise from the imaging signal output fromthe sensor unit 244 a and performs A/D conversion on the imaging signal;a P/S converter 244 c that performs parallel-serial conversion on theimaging signal (a digital signal) output from the AFE unit 244 b andtransmits the converted imaging signal to the outside (the processingdevice 3); a timing generator 244 d that generates the driving timing ofthe sensor unit 244 a, and the pulses for various signal processes inthe AFE unit 244 b and P/S converter 244 c; and an imaging controller244 e that controls the operation of the first image sensor 244A or thesecond image sensor 244B. Each of the first image sensor 244A and thesecond image sensor 244B is implemented with a Complementary Metal OxideSemiconductor (CMOS) image sensor.

The sensor unit 244 a includes a light receiving unit 244 f and areading unit 244 g. In the light receiving unit 244 f, a plurality ofpixels each having a photodiode and a capacitor is arranged in a matrixform. The photodiode accumulates electric charge depending on the amountof light. The capacitor converts the electric charge transferred fromthe photodiode into a voltage level. Each of the pixels performsphotoelectric conversion on the light from the optical system 243A or243B to generate an electric signal. The reading unit 244 g sequentiallyreads the electric signals generated by the pixels that are arbitrarilyset as reading targets among the plurality of pixels in the lightreceiving unit 244 f, and outputs the electric signals as imagingsignals. A color filter is provided on a light-receiving surface of thelight receiving unit 244 f. The reading unit 244 g sequentially reads,for each horizontal line, the electric signals generated by theplurality of pixels arranged in a matrix form.

The AFE unit 244 b includes: a noise reduction circuit that reduces thenoise contents included in the analog imaging signals, for example,using a Correlated Double Sampling method; an Automatic Gain Control(AGC) circuit that maintains the output at a constant level by adjustingthe amplification factor (gain) of the imaging signal (the electricsignal); and an A/D conversion circuit that performs A/D conversion onthe imaging signal output through the AGC circuit.

The imaging controller 244 e controls each of the operations of thefirst image sensor 244A or the second image sensor 244B in accordancewith the control signal on the received setting data or thesynchronization control. The imaging controller 244 e, for example,outputs the reading signal to the reading unit 244 g and controls theoutput of the electric signal output from each pixel by the pixel. Theimaging controller 244 e includes, for example, a Central ProcessingUnit (CPU) or a register that stores various programs.

The operating unit 22 is provided with: a curving knob 221 that curvesthe curved portion 25 up and down, and right and left; a treatment toolinsertion unit 222 for inserting a treatment tool such as biopsyforceps, an electrical scalpel, or an inspection probe into the bodycavity of the subject; and a plurality of switches 223 that areoperation input units configured to input the instruction signals forthe operations of peripheral devices such as an air feeding unit, awater feeding unit, and an image display control in addition to theprocessing device 3 and the light source device 4. The treatment toolinserted from the treatment tool insertion unit 222 extends outside froman opening portion (not illustrated) through a treatment tool channel(not illustrated) of the tip portion 24.

The operating unit 22 further includes a first communication controller224, a second communication controller 225, a first clock generator 226,and a second clock generator 227. The first communication controller 224controls the driving timing at which the first image sensor 244A isdriven in accordance with the setting data received from the processingdevice 3 or the control signal on synchronization control. The secondcommunication controller 225 controls the driving timing at which thesecond image sensor 244B is driven in accordance with the setting datareceived from the processing device 3 or the control signal onsynchronization control. The first clock generator 226 generates a clocksignal (a first clock signal) to drive the first communicationcontroller 224. The second clock generator 227 generates a clock signal(a second clock signal) to drive the second communication controller225. Note that the first clock generator 226 can be embedded in thefirst communication controller 224 and the second clock generator 227can be embedded in the second communication controller 225. Amicrocomputer having a clock generating circuit is used for the firstcommunication controller or the second communication controller, forexample.

The universal cord 23 incorporates at least the light guide 241 and acable assembly 245 having one or more signal lines. The cable assembly245 includes a signal line to transmit and receive the setting data, anda signal line to transmit and receive an imaging signal.

The configuration of the processing device 3 will be described next. Theprocessing device 3 includes a first S/P converter 301A, a second S/Pconverter 301B, an image processing unit 302, a luminance detecting unit303, a light adjusting unit 304, a driving signal generator 305, aninput unit 306, a storage unit 307, a control unit 308, and a referenceclock generator 309 (a third clock generator).

The first S/P converter 301A and the second S/P converter 301B preformserial-parallel conversion on the imaging signals (digital signals)received from the tip portion 24 (the first image sensor 244A and thesecond image sensor 244B), respectively, and output the convertedimaging signals to the image processing unit 302.

The image processing unit 302 generates image signals to be displayedwith the display device 5 based on the imaging signals input from thefirst S/P converter 301A and the second S/P converter 301B. The imageprocessing unit 302 generates image signals including an in-vivo imageto be displayed by processing the imaging signals in an predeterminedimage process. The image process includes a synchronization process, anoptical black subtraction process, a white balance adjusting process, acolor matrix operation process, a gamma correction process, a colorreproduction process, an edge enhancement process, a synthesizingprocess for synthesizing a plurality of image data items, and a formatconversion process. The image processing unit 302 generates imagesignals including a three-dimensional image, or a two-dimensional imagehaving a large number of pixels based on the imaging signals generatedby the first image sensor 244A and the second image sensor 244B. Theimage processing unit 302 further outputs the imaging signals input fromthe first S/P converter 301A and the second S/P converter 301B to thecontrol unit 308 or the luminance detecting unit 303.

The luminance detecting unit 303 detects the luminance levelcorresponding to each pixel from the image signals of RGB componentsoutput from the image processing unit 302. The luminance detecting unit303 records the detected luminance level in an internal memory, andoutputs the detected luminance level to the control unit 308. Theluminance detecting unit 303 calculates a gain adjusting value and theamount of light irradiation based on the detected luminance level. Theluminance detecting unit 303 outputs the calculated gain adjusting valueto the image processing unit 302 while outputting the calculated amountof light irradiation to the light adjusting unit 304.

The light adjusting unit 304 sets the amount of light generated by thelight source device 4 and the light emitting timing in accordance withthe amount of light irradiation calculated by the luminance detectingunit 303 under the control by the control unit 308. Then, the lightadjusting unit 304 transmits the control signals including the setconditions to the light source device 4.

The driving signal generator 305 generates a drive synchronizationsignal for driving the first image sensor 244A and the second imagesensor 244B, and transmits the drive synchronization signal to the firstcommunication controller 224 and the second communication controller225.

The driving signal generator 305 includes a reference synchronizationsignal generator 305 a, and an imaging synchronization signal generator305 b. The reference synchronization signal generator 305 a generatessynchronization signals based on the clock signal generated by thereference clock generator 309. The synchronization signals generated bythe reference synchronization signal generator 305 a include referencesynchronization signals that are references for the operation of eachunit in the processing device 3 and the operations of the endoscope 2and the light source device 4.

The imaging synchronization signal generator 305 b generates an imagingsynchronization signal to drive the first image sensor 244A and thesecond image sensor 244B based on the clock signal generated by thereference clock generator 309, and outputs the imaging synchronizationsignal to the first communication controller 224 and the secondcommunication controller 225. Specifically, the imaging synchronizationsignal generator 305 b outputs an imaging synchronization signal. Theimaging synchronization signal is a trigger for determining the imagingtiming for the first image sensor 244A and the second image sensor 244Bto start an imaging operation in response to the processing time of thefirst communication controller 224 and the second communicationcontroller 225. The imaging timing is the starting timing at which animaging operation starts. The imaging operation is for reading andobtaining the electric signals of a frame in an image.

The input unit 306 receives the input of the various signals such as anoperation instruction signal that instructs the operation of theendoscopic system 1.

The storage unit 307 is implemented with a semiconductor memory such aflash memory or a Dynamic Random Access Memory (DRAM). The storage unit307 stores various programs for operating the endoscopic system 1, andthe data including various parameters necessary for the operation of theendoscopic system 1.

The control unit 308 includes a CPU. The control unit 308 controls thedriving of each of the elements including the tip portion 24 and thelight source device 4, and controls the input and output of informationto and from each of the elements. The control unit 308 transmits thesetting data for controlling the imaging process to the imagingcontroller 244 e through a predetermined signal line in the cableassembly 245. The setting data includes the imaging rate (frame rate) ofeach of the first image sensor 244A and the second image sensor 244B,settings for an electronic shutter or gain, the instruction informationfor instructing the reading rate at which the pixel information is readfrom an arbitrary pixel in the sensor unit 244 a, and the transmittingcontrol information of the pixel information read by the AFE unit 244 b.

The reference clock generator 309 generates a clock signal (a thirdclock) that is the reference for the operation of each element in theendoscopic system 1, and provides the generated clock signal to eachelement in the endoscopic system 1. In the first embodiment, a clocksignal that the reference clock generator 309 generates is precise incomparison with the clock signals that the first clock generator 226 andthe second clock generator 227 generate. Specifically, the oscillator ofthe reference clock generator 309 create a precise frequency incomparison with the frequencies created with the oscillators of thefirst clock generator 226 and the second clock generator 227.

The configuration of the light source device 4 will be described next.The light source device 4 includes a white light source 41, a lightsource controller 42, and a Light Emitting Diode (LED) driver 43.

The white light source 41 includes a white LED and generates a whiteillumination light under the control by the light source controller 42.

The light source controller 42 controls the amount of current to besupplied to the white light source 41 in accordance with the controlsignal transmitted from the light adjusting unit 304.

The LED driver 43 makes the white light source 41 generate theillumination light by supplying the current to the white light source 41under the control by the light source controller 42. The light generatedby the white light source 41 is emitted from the front end of the tipportion 24 through the light guide 241 to the outside.

Note that a special light source to generate an excitation light thatexcites a fluorescent material introduced in the subject can be providedin the light source device 4. The special light source generates, forexample, an infrared light. The special light source can generate, asspecial light, light of any one of color components red, green, and blueat a wavelength band that is different from the wavelength band of thewhite luminance light and narrowed with a narrow band pass filter. Thespecial light can be, for example, a Narrow Band Imaging (NBI)illumination light of two types of blue light and green light atnarrowed bandwidths so that the special light can easily be absorbed inhemoglobin in the blood.

The display device 5 has a function to receive the in-vivo imagegenerated by the processing device 3 through an image cable and displaysthe image. The display device 5 includes a display such as a liquidcrystal display, or an organic Electro Luminescence (EL) display.

Note that the first image sensor 244A, the second image sensor 244B, thefirst communication controller 224, the second communication controller225, the first clock generator 226, the second clock generator 227, thereference synchronization signal generator 305 a, and the imagingsynchronization signal generator 305 b are used to constitute theimaging device (the endoscopic device) in the first embodiment.

The synchronization control of the imaging timing in the endoscopicsystem 1 will be described next with reference to FIGS. 3 and 4. FIG. 3is a timing chart of the control timing of the endoscopic systemaccording to the first embodiment. FIG. 4 is a timing chart of thecontrol timing of the endoscopic system according to the firstembodiment, illustrating a part of FIG. 3 in more detail.

The first image sensor 244A and the second image sensor 244B alternatelyrepeat the exposure on the light receiving unit 244 f and the reading ofan electric signal of a horizontal line with the reading unit 244 g soas to obtain the imaging signals including the in-vivo image of thesubject. The first image sensor 244A and the second image sensor 244Balternately read each of first to n-th horizontal lines (of a frame) atdifferent points in time. In the first embodiment, a period required forthe exposure process and reading process with the first image sensor244A and the second image sensor 244B is referred to as a field. Thereading process is for reading the electric signal generated by theexposure process. In other words, for example, an exposure process and areading process for obtaining the electric signals (the imaging signals)of a frame included in an image are performed in a field.

The field is switched from a field 1 to a field 2 at an internalsynchronization timing (a reference synchronization signal) in theprocessing device 3. The reference timing based on the synchronizationtiming (the reference synchronization signal) sometimes differs from adesired timing at which the image sensor starts the reading process. Inlight of the foregoing, the control unit 308 transmits thesynchronization signal generated in the imaging synchronization signalgenerator 305 b to the first communication controller 224 and the secondcommunication controller 225.

The first communication controller 224 and the second communicationcontroller 225 start a synchronization control communication, using thereference synchronization signal from the driving signal generator 305as a trigger for the communication. The synchronization controlcommunication is for synchronization control that determines an imagingtiming (vertical synchronization timing) and includes the settings(register settings) for the operation conditions of the first imagesensor 244A and the second image sensor 244B. At that time, the firstcommunication controller 224 starts the synchronization controlcommunication after counting a predetermined period of time from thesynchronization timing based on the clock signal generated in the firstclock generator 226. Meanwhile, the second communication controller 225starts the synchronization control communication after counting apredetermined period of time from the synchronization timing based onthe clock signal generated in the second clock generator 227. In theregister settings, the control unit 308 transmits the setting data, forexample, in a publicly known communication standard such as I²C or SPIso that various settings for each image sensor (for example, thesettings for controlling the luminance of the electronic shutter, thedesignation of the device, and the designation of the address) areconfigured.

After that, the imaging synchronization signal generated by the imagingsynchronization signal generator 305 b is transmitted to the endoscope 2(the first communication controller 224 and the second communicationcontroller 225). The imaging synchronization signal transmitted from theimaging synchronization signal generator 305 b is used as a trigger forthe control to complete the synchronization control communication, and asignal for determining the last communication in the synchronizationcontrol communication by the first communication controller 224 and thesecond communication controller 225.

Specifically, the imaging synchronization signal generator 305 b countsthe elapsed period between the synchronization timing of the processingdevice 3 and the timing of the last communication in the synchronizationcontrol communication by the first communication controller 224, and theelapsed period between the synchronization timing of the processingdevice 3 and the timing of the last communication in the synchronizationcontrol communication by the second communication controller 225. Then,the imaging synchronization signal generator 305 b outputs an imagingsynchronization signal at a timing determined in accordance with theamount of the time lag between the two elapsed periods (the number ofclocks) and the timing of completing the synchronization controlcommunications. For example, each of the first communication controller224 and the second communication controller 225 performs the lastcommunication, using the reception of the imaging synchronization signalas a trigger. The imaging synchronization signal generator 305 b outputsthe imaging synchronization signal after counting a predetermined periodof time from the reference timing based on the synchronization timing(the reference synchronization signal). The reference timing can be anarbitrary timing, for example, the timing at which the referencesynchronization signal is output, or the timing at which the firstcommunication controller 224 or the second communication controller 225starts the synchronization control communication. Note that the imagingsynchronization signal generator 305 b can determine the number ofclocks (the elapsed period) by counting the period elapsed in thesynchronization control communication previously performed, or bycounting the period elapsed in the communication performed when theendoscopic system 1 starts.

As illustrated in FIG. 4, the first communication controller 224performs the synchronization control communication based on thesynchronization timing of the processing device 3, and suspends thecommunication until just before the last communication in thesynchronization control communication. The second communicationcontroller 225 performs the synchronization control communication basedon the timing counted with the clocks generated by the second clockgenerator 227, and suspends the communication until just before the lastcommunication in the synchronization control communication. Thefrequency of the clock generated in first clock generator 226 slightlydiffers from the frequency of the clock generated in the second clockgenerator 227. In FIG. 4, there is a time lag in counting between thesecond communication controller 225 and the first communicationcontroller 224 even if the first communication controller 224 and thesecond communication controller 225 start a communication at the sametime. Thus, the second communication controller 225 performs thecommunication at a timing later than a timing in the first communicationcontroller 224. The first communication controller 224 and the secondcommunication controller 225 perform the last communication in thesynchronization control communication, using the imaging synchronizationsignal from the imaging synchronization signal generator 305 b as atrigger.

Specifically, when the signal is latched with the falling edge of thelast clock in the communication, the first communication controller 224generates a falling clock with the imaging synchronization signal fromthe imaging synchronization signal generator 305 b as illustrated inFIG. 4. The second communication controller 225 generates a fallingclock, using the imaging synchronization signal as a trigger. Generatingthe falling clocks determines the vertical synchronization timing(imaging timing) of the first image sensor 244A and the second imagesensor 244B, and switches the field. When the field is switched, thereading unit 244 g starts a reading process.

The first communication controller 224 and the second communicationcontroller 225 performed the last communication in the synchronizationcontrol communication, using the imaging synchronization signal countedwith the reference clock as a trigger as described above. Thus, thepoints in time of completing synchronization control communication ofthe first communication controller 224 and the second communicationcontroller 225 are approximately identical. This can control thesynchronization between the first communication controller 224 and thesecond communication controller 225 with a high degree of accuracy evenif there is a time lag between the periods counted with the firstcommunication controller 224 and the second communication controller225. Note that the timing at which the imaging synchronization signal isinput is shorter than the period between the start and completion of thesynchronization control communication by the first communicationcontroller 224 and the second communication controller 225. In otherwords, the imaging synchronization signal is preferably output after thecommunications start.

According to the first embodiment, the first communication controller224 and the second communication controller 225 perform the lastcommunication in the synchronization control communication, using theimaging synchronization signal as a trigger. This determines thevertical synchronization timing (the imaging timing) of each of thefirst image sensor 244A and the second image sensor 244B. This cansynchronize a plurality of image sensors with a high degree of accuracy.

In the first embodiment, for example, the first communication controller224 counts a predetermined period of time based on the clocks generatedby the first clock generator 226 so that the first image sensor 244Astarts the synchronization control communication. Note that, however,the first communication controller 224 can start the communication, forexample, at the communication starting timing (not illustrated)transmitted from the control unit 308. This can control also thecommunication starting timing with a high degree of accuracy althoughincreasing the number of control lines.

In the first embodiment, the first communication controller 224 and thesecond communication controller 225 perform a synchronization controlcommunication in every field. However, the first communicationcontroller 224 and the second communication controller 225 can performthe communication every several fields or in predetermined fields.

In the first embodiment, the field is switched at the falling of thelast pulse. However, the field can be switched after several clocks arecounted from the falling of the last pulse.

In the first embodiment, the imaging synchronization signal is thetrigger for the last communication. However, a falling clock can begenerated just after the imaging synchronization signal is received, orthe falling clock can be generated after several clocks are counted. Thetiming of the last communication can be controlled in any way as long asthe reception of the imaging synchronization signal is used as thetrigger.

In the first embodiment, the processing device 3 is provided with theimaging synchronization signal generator 305 b. However, a counter canbe provided in the endoscope 2, for example, in the connector 23 a. Insuch a case, a clock generator corresponding to the reference clockgenerator 309 is preferably provided in the endoscope 2.

Second Embodiment

The second embodiment of the present invention will be described next.FIGS. 5A and 5B are schematic block diagrams of the configuration of anendoscopic system according to the second embodiment. The same elementsas those in the above-described embodiment will be denoted by the samereference signs. In the second embodiment, a horizontal synchronizationsignal is extracted from the obtained imaging signals. The verticalsynchronization timing is determined in accordance with the horizontalsynchronization timing of a first image sensor 244A and a second imagesensor 244B. Then, the field is switched.

An endoscopic system 1 a according to the second embodiment includes anendoscope 2, a light source device 4, a display device 5, and aprocessing device 3 a. The processing device 3 a includes a firstsynchronization signal extracting unit 310A and a second synchronizationsignal extracting unit 310B in addition to the elements of theprocessing device 3. Note that the vertical synchronization timing ofthe first image sensor 244A and the second image sensor 244B iscontrolled by the horizontal synchronization timing in the secondembodiment. Specifically, the register settings for each image sensorare configured. After the register settings is completed, asynchronization signal is generated in each image sensor based on thefirst horizontal synchronization timing. Each image sensor is driven inaccordance with the generated synchronization signal. When the registersettings are completed at different points in time, for example, whenthe first image sensor 244A completes the setting before the horizontalsynchronization signal and the second image sensor 244B completes thesetting after the horizontal synchronization signal, this generates adifference in timing of driving each of the image sensors by onehorizontal synchronization period. The first image sensor 244A, thesecond image sensor 244B, a first communication controller 224, a secondcommunication controller 225, a first clock generator 226, a secondclock generator 227, a reference synchronization signal generator 305 a,an imaging synchronization signal generator 305 b, and thesynchronization signal extracting unit (the first synchronization signalextracting unit 310A and the second synchronization signal extractingunit 310B) are used to constitute an imaging device in the secondembodiment.

First, the first synchronization signal extracting unit 310A and thesecond synchronization signal extracting unit 310B obtain the imagingsignals generated in the endoscope 2 through a first S/P converter 301Aand a second S/P converter 301B, respectively. The first synchronizationsignal extracting unit 310A and the second synchronization signalextracting unit 310B separate the imaging signals into the image signalsand the synchronization signals, and extract the horizontalsynchronization signal from the separated signals.

The imaging synchronization signal generator 305 b generates ahorizontal synchronization signal in accordance with an interval betweenadjacent pulses in the horizontal synchronization signal extracted witheach of the first synchronization signal extracting unit 310A and thesecond synchronization signal extracting unit 310B. Specifically, theimaging synchronization signal generator 305 b generates an imagingsynchronization signal. The imaging synchronization signal is outputsuch that the timings of completing the communications of the firstcommunication controller 224 and the second communication controller 225are located at the same interval between the pulses. The imagingsynchronization signal according to the second embodiment is the triggerfor the control of the completion of the synchronization controlcommunication. Specifically, when the imaging synchronization signal isreceived, the reception is used as the trigger for the lastcommunication.

FIG. 6 is a timing chart of the control timing for controlling theendoscopic system according to the second embodiment. The firstcommunication controller 224 and the second communication controller 225start a synchronization control communication based on the clock thateach of the first communication controller 224 and the secondcommunication controller 225 counts, or start a synchronization controlcommunication based on the synchronization timing of the processingdevice 3, similarly to the first embodiment.

When a synchronization signal is output from the imaging synchronizationsignal generator 305 b in the synchronization control communication, thefirst communication controller 224 and the second communicationcontroller 225 use the imaging synchronization signal as a trigger, andperform the synchronization control communication, for example, whilesuspending the synchronization control communication for a period ofseveral clocks. Specifically, the first communication controller 224 andthe second communication controller 225 delay the timing of completingcommunication by suspending the communication for a period of a setnumber of clocks until the first communication controller 224 and thesecond communication controller 225 perform the last communication inresponse to an imaging synchronization signal from the imagingsynchronization signal generator 305 b, as illustrated in FIG. 6. Notethat the first communication controller 224 and the second communicationcontroller 225 that suspend the communication just before the lastcommunication in a synchronization control communication can perform thelast communication and complete the communication, using the imagingsynchronization signal as a trigger. This makes it possible to adjustthe timings of completing the communications of the first image sensor244A and the second image sensor 244B such that the timings are locatedin the same interval between the pulses of the horizontalsynchronization signal (for example, at an interval nH in FIG. 6) and donot overlap with (do not match) the horizontal synchronization pulses.Thus, the horizontal synchronization timings for determining thevertical synchronization timings between the first image sensor 244A andthe second image sensor 244B are matched. When the horizontalsynchronization timings are matched, the vertical synchronizationtimings of the first image sensor 244A and the second image sensor 244Bare also matched. The field can be switched with the correspondingvertical synchronization timing. After the field is switched, thereading unit 244 g starts a reading process.

When the vertical synchronization timing of the first image sensor 244Aand the vertical synchronization timing of the second image sensor 244Bare controlled by the horizontal synchronization timing, the firstcommunication controller 224 and the second communication controller 225adjust the timing of completing the synchronization control, using theimaging synchronization signal as a trigger. It is therefore possible tocontrol the synchronization between the first communication controller224 and the second communication controller 225 with a high degree ofaccuracy even if there is a difference in counts between the firstcommunication controller 224 and the second communication controller225.

According to the second embodiment, the first communication controller224 and the second communication controller 225 adjust the completion ofthe synchronization control by counting a predetermined number ofclocks, using the imaging synchronization signal as a trigger. Thisleads to the matching between the horizontal synchronization timings andto the matching between the vertical synchronization timings. It istherefore possible to synchronize a plurality of image sensors with ahigh degree of accuracy.

In the second embodiment, the processing device 3 includes the imagingsynchronization signal generator 305 b, the first synchronization signalextracting unit 310A and the second synchronization signal extractingunit 310B. However, the counter and the synchronization signalextracting units can be provided in the endoscope 2, for example, in theconnector 23 a. In such a case, a clock generator corresponding to thereference clock generator 309 is preferably provided in the endoscope 2.The first synchronization signal extracting unit 310A and the secondsynchronization signal extracting unit 310B obtain the imaging signalsfrom the AFE unit 244 b or the P/S converter 244 c, and extract thehorizontal synchronization signals.

In the second embodiment, the completion of the synchronization signalsmay occur at different points in time as long as the timings ofcompleting the synchronization control of the first communicationcontroller 224 and the second communication controller 225 are locatedin the same interval between the pulses in the horizontalsynchronization signal.

In the first and second embodiments, the vertical synchronization timingis determined with the timing at which the control communication iscompleted (or the horizontal synchronization timing just after thecompletion). Any data item in the control communication can be set asthe timing data for determining the vertical synchronization timinginstead of the timing at which the control communication is completed.In such a case, the imaging synchronization signal is transmitted sothat the setting data is set at the timing (for example, at an intervalbetween the horizontal synchronization pulses).

Note that, a rotation filter can be arranged on the light path on whichthe white light source 41 emits a white light in the first and secondembodiments. The rotation filter includes a plurality of filters to makeonly light at predetermined wavelength bands in the white lightpenetrate by rotating the filters. The provided rotation filter makesthe light having wavelength bands of the red light (R), green light (G),and blue light (B) sequentially penetrate so that the light are emitted.This can sequentially emit the red light (R illumination), green light(G illumination), and blue light (B illumination) at narrowed bandwidthsin the white light that the white light source 41 emits (W illumination)to the endoscope 2 (in a frame sequential method). In the emission,performing the imaging control as described above can reduce the colordeviation between the images.

In the first and second embodiments, the reference synchronizationsignal (the synchronization timing) for causing the first image sensor244A and the second image sensor 244B to start the imaging operation isgenerated based on the clock signal generated by the reference clockgenerator 309. However, the reference synchronization signal can begenerated based on the clock signal generated by the first clockgenerator 226, the second clock generator 227, or an external clockgenerator.

The synchronization between the two image sensors is controlled in thefirst and second embodiments. However, the imaging process can also becontrolled when three or more image sensors are provided.

According to some embodiments, it is possible to synchronize a pluralityof image sensors with a high degree of accuracy.

As described above, the imaging device and the endoscopic deviceaccording to some embodiments are useful for synchronizing a pluralityof image sensors with a high degree of accuracy.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and representative embodiments shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

What is claimed is:
 1. An imaging device comprising: first and secondimage sensors configured to receive light and to perform photoelectricconversion on the received light to generate electric signals; a firstcommunication controller configured to be connected to the first imagesensor to perform communication with the first image sensor and tocontrol the communication to perform operating control on the firstimage sensor; a first clock generator configured to generate a firstclock signal that is a reference for operation of the firstcommunication controller; a second communication controller configuredto be connected to the second image sensor to perform communication withthe second image sensor and to control the communication to performoperating control on the second image sensor; a second clock generatorconfigured to generate a second clock signal that is a reference foroperation of the second communication controller; a referencesynchronization signal generator configured to generate a referencesynchronization signal; and an imaging synchronization signal generatorconfigured to generate an imaging synchronization signal that is atrigger for determining timings of imaging by the first and second imagesensors, and to output the imaging synchronization signal to the firstand second communication controllers at a timing when a predeterminedperiod of time has elapsed from a reference timing based on thereference synchronization signal, wherein when the first and secondcommunication controllers perform synchronization control communicationsfor synchronizing the timings of imaging by the first and second imagesensors, the first and second communication controllers are configuredto determine the timings of imaging by the first and second imagesensors using the imaging synchronization signal output from the imagingsynchronization signal generator as a trigger.
 2. The imaging deviceaccording to claim 1, further comprising a third clock generatorconfigured to generate a third clock signal with higher precision offrequency than the first and second clock signals, wherein the referencesynchronization signal generator is configured to generate the referencesynchronization signal based on the third clock signal.
 3. The imagingdevice according to claim 1, further comprising a synchronization signalextracting unit configured to extract a horizontal synchronizationsignal from the electric signals generated by the first and second imagesensors, wherein the imaging synchronization signal generator isconfigured to generate the imaging synchronization signal such thattimings of completing the synchronization control communications betweenthe first and second image sensors and the first and secondcommunication controllers are located in a same interval betweenhorizontal synchronization pulses and do not overlap with the horizontalsynchronization pulses.
 4. The imaging device according to claim 1,wherein a timing of inputting the imaging synchronization signal isshorter than a period of time between when the first and secondcommunication controllers start the synchronization controlcommunications and when the first and second communication controllerscomplete the synchronization control communications.
 5. An endoscopicdevice comprising: an insertion unit that has an elongated shape and isconfigured to be inserted into a living body; first and second imagesensors configured to receive light and to perform photoelectricconversion on the received light to generate electric signals; a firstcommunication controller configured to be connected to the first imagesensor to perform communication with the first image sensor and tocontrol the communication to perform operating control on the firstimage sensor; a first clock generator configured to generate a firstclock signal that is a reference for operation of the firstcommunication controller; a second communication controller configuredto be connected to the second image sensor to perform communication withthe second image sensor and to control the communication to performoperating control on the second image sensor; a second clock generatorconfigured to generate a second clock signal that is a reference foroperation of the second communication controller; a referencesynchronization signal generator configured to generate a referencesynchronization signal; and an imaging synchronization signal generatorconfigured to generate an imaging synchronization signal that is atrigger for determining timings of imaging by the first and second imagesensors, and to output the imaging synchronization signal to the firstand second communication controllers at a timing when a predeterminedperiod of time has elapsed from a reference timing based on thereference synchronization signal, wherein when the first and secondcommunication controllers perform synchronization control communicationsfor synchronizing the timings of imaging by the first and second imagesensors, the first and second communication controllers are configuredto determine the timings of imaging by the first and second imagesensors using the imaging synchronization signal output from the imagingsynchronization signal generator as a trigger.